The invention is in the field of electronic reproduction technology and is directed to a method for the point-by-point and line-by-line exposing of recording material with a light beam, and is also directed to an electronic exposing unit, also called an exposer, recorder or image setter.
In a recorder, a light beam modulated by a video signals is conducted point-by-point and line-by-line across a recording material to be exposed. The recording material is thereby fixed on a holder that moves relative to the light beam. Given an inside-the-drum device, the recording material is fixed on a stationary holder shaped like a cylindrical segment or on an exposure trough, and the light beam is conducted across the recording material point-by-point and line-by-line with a rotating light beam deflection means. However, the recorder can also be designed as a drum device or flat bed device.
A laser is often employed as a light source for generating the light beam. The modulation of the light beam dependent on the video signal occurs with a modulator, for example with an acousto-optical modulator. In the traditional technology, the drive of the modulator with the video signal occurs such that the modulator is activated line-by-line within exposure time spans wherein the light beam sweeps the lines to be recorded on the recording material and is deactivated during return time spans wherein the light beam is conducted to the next line to be exposed.
In a traditional recorder, back reflections from the modulator or the light beam deflection unit can disadvantageously occur in the direction toward the light source, and these must be prevented in order to achieve a good recording quality. Beyond this, a high efficiency of the modulator is required so that a light beam with high luminous power is available for exposing the recording medium. Further, the components that are employed must have optimally constant operating properties since, for example due to heating of the components, the optical properties of the light beam can vary, this in turn diminishing the recording quality.